The present invention concerns centrifugal processing apparatus, and more particularly, apparatus employing umbilical tubing which is rotated with respect to a stationary base.
Centrifugal processing systems are used in many fields. In one important field of use, a liquid having a suspended mass therein is subjected to centrifugal forces to obtain separation of the suspended mass.
As a more specific example, although no limitation is intended herein, in recent years the long term storage of human blood has been accomplished by separating out the plasma component of the blood and freezing the remaining red blood cell component in a liquid medium, such as glycerol. Prior to use, the glycerolized red blood cells are thawed and pumped into the centrifugating wash chamber of a centrifugal liquid processing apparatus. While the red blood cells are being held in place by centrifugation, they are washed with a saline solution which displaces the glycerol preservative. The resulting reconstituted blood is then removed from the wash chamber and packaged for use.
The aforementioned blood conditioning process, like other processes wherein a liquid is caused to flow through a suspended mass under centrifugation, necessitates the transfer of solution into and out of the rotating wash chamber while the chamber is in motion. Thus while glycerolized red blood cell and saline solution are passed into the wash chamber, waste and reconstituted blood solutions are passed from the chamber. To avoid contamination of these solutions, or exposure of persons involved in the processing operation to the solutions, the transfer operations are preferably carried out within a sealed flow system.
One type of centrifugal processing system which is well adapted for the aforementioned blood conditioning process uses the principles of operation described in Dale A. Adams U.S. Pat. No. 3,586,413. The apparatus of the Adams patent establishes fluid communication between a rotating chamber and stationary reservoirs through a flexible interconnecting umbilical cord without the use of rotating seals, which are expensive to manufacture and which add the possibility of contamination of the fluid being processed.
The primary embodiment of the Adams patent comprises a rotating platform which is supported above a stationary surface by means of a rotating support. A tube is connected to the stationary support along the axis of the rotating platform and the rotating support, with the tube extending through the rotating support and having one end fastened to the axis of the rotating platform. A motor drive is provided to drive both the rotating platform and the rotating support in the same relative direction at speeds in the ratio of 2:1, respectively. It has been found that by maintaining this speed ratio, the tube will be prevented from becoming twisted. An improvement with respect to this principle of operation, comprising a novel drive system for a centrifugal liquid processing system, is disclosed in Khoja, et al. U.S. Pat. No. 3,986,442. In the Khoja, et al. patent, a novel drive system is provided for driving a rotor assembly at a first speed and a rotor drive assembly at one-half the first speed, in order to prevent an umbilical tube from becoming twisted.
It has been found that significant frictional heating and drag is experienced by the umbilical tube as it contacts guide portions of the centrifuge. To alleviate these difficulties, lubrication has been provided which is helpful, but such lubrication requires frequent replacement.
Some constructions have utilized a free rotating guide through which the umbilical tube extends. Typically the tube at high speed may rotate about the centrifuge axis at 1,500 rpm. Since the guide is freely rotating at a speed determined by the surface speed of the umbilical tube at the point of highest loading, surface speeds at all other points along the free rotating guide will be mismatched, causing frictional heating and drag.
It is, therefore, an object of the invention to provide means for alleviating the friction heating and drag experienced by the umbilical tube during rotation thereof as it contacts guide portions of the centrifuge.
Another object of the present invention is to provide a frictional heating and drag reducing system which does not require lubrication for its operability.
A further object of the present invention is to provide a frictional heating and drag reducing system for the umbilical tube of a rotating centrifuge, in which special treatment of metal parts is unnecessary.
A still further object of the present invention is to provide a friction reducing method for rotating umbilical tubing in a rotating centrifuge in which build-up of abrasion products resulting from low friction surfaces is avoided.
Another object of the present invention is to provide a friction reducing system which is efficient in operation and relatively inexpensive to construct.
Other objects and advantages of the present invention will become apparent as the description proceeds.